The present invention relates to a method for operating a cutting dredger in open water, in particular to control of a ground reaction force during dredging operations, the dredger comprising;                a floating body,        an elongate cutter ladder having a cutting head at its lowerable free end for dredging, which cutter ladder is hingeably coupled to the floating body and hingeable between an upwards position and a cutting position wherein the cutting head engages matter to be cut away at the floor of a body of water,        
Such a method is known from US2005268499 which relates to method and apparatus for pumping with a dredge. Herein it is disclosed to apply a predetermined amount of load force by the head against the bottom. Herein, a winch and cable and the controller are operated to lift some of the head weight until the desired predetermined head force is applied to the bottom. It is a disadvantage that head weight can only be lifted.
In general, it is known to raise and lower a ladder connected to the hull of a dredger by a hydraulic cylinder like for instance in U.S. Pat. Nos. 3,470,633, 4,095,545A, 4,628,623A and 2,850,814. Typically, these dredgers have a relative short ladder and are not suitable to operate in open water and instead intend to operate in areas where room is restricted and/or areas with no or very small waves, like in a port or harbour. These hydraulic cylinders are not operated while dredging. It is however known to operate a ram cylinder to provide crowding action for tough digging. This ram cylinder is coupled with a relative short ladder not suitable for open water. Open water here means water with possibly significant wave height.
It is also known, like in U.S. Pat. No. 2,963,801A, to hydraulically drive a cutter ladder during swing motion, which is a lateral motion with respect to vertical motion.
US 2005/0268499 A relates to an environmental dredging method having a suction head for removing a contaminated layer from a bottom of a body of water. A predetermined amount of load force may be applied by the suction head against the bottom. Herein, a winch and cable and the controller are operated to lift some of the suction head weight until the desired predetermined head force is applied to the bottom. Such a suction head suspended from a cable does not suffice for controlling a ground reaction force of a cutting dredger.
U.S. Pat. No. 3,777,376 (A) discloses a dredging apparatus for use in heavy seas having a barge and an articulated ladder. U.S. Pat. No. 3,777,376 relates to positioning of ladder parts in that a lower ladder part is angularly movable relative to the upper ladder part, and means are provided for adjustably positioning said first ladder part at a selected angle relative to said barge. The ladder is moved between its working and non-working positions by a winch carrying a cable 87. Such a cable does not suffice for controlling a ground reaction force of a cutting dredger.